The invention relates to controlling power states of a computer.
The main power switch, located on a computer's housing, has typically been used to power the computer on and off. In a continuing effort to make it more convenient for a user to control the power state of a computer and to reduce power consumption, other ways of powering down the computer have been developed. For example, the Advanced Power Management (APM) (Version 1.2) standard has defined various low power states (including suspend states and intermediate power savings states) that the computer can transition to. Operating systems (such as Windows.RTM. from Microsoft Corporation) that support an APM suspend state (e.g., Soft-Off) allow a user to place the computer into the Soft-Off state directly from the graphical user interface of the operating system (such as from the Start menu in the Windows 95.RTM. user interface).
An example of a hardware device that can cooperate with the Windows.RTM. operating system to control the computer's power states is the 82371AB PCI-TO-ISA/IDE XCELERATOR (PIIX4) sold by Intel Corporation, which includes a system power management controller to manage transitions of the computer power state, including the Soft-Off state.
However, in addition to use of an operating system interface, other mechanisms for controlling the computer system's power state are needed to increase user convenience in placing a computer system into a reduced power state.